iRule to redirect URL based on source address

You could use a simple iRule like this

when HTTP_REQUEST {
    if {([HTTP::uri] equals "/admin") || ([HTTP::uri] equals "/admin2")} {
        if {!([IP::client_addr] equals "10.0.0.1")} {
            HTTP::redirect https://mywebsite.co.uk
        }
    }
}

You could also use a datagroup to store your IP addresses if you plan on using more than one:

when HTTP_REQUEST {
    if {([HTTP::uri] equals "/admin") || ([HTTP::uri] equals "/admin2")} {
        if {!([class match [IP::client_addr] equals "my_datagroup"])} {
            HTTP::redirect https://mywebsite.co.uk
        }
    }
}

You can take this a step further and add the URIs to a datagroup too:

 when HTTP_REQUEST {
    if {[class match [HTTP::uri] equals "my_uri_datagroup"]} {
        if {!([class match [IP::client_addr] equals "my_ip_datagroup"])} {
            HTTP::redirect https://mywebsite.co.uk
        }
    }
}